This invention relates to an optical space switch device which provides variable interconnection of one- or two-dimensionally spatially multiplexed optical signals.
In recent years, the requirement has been and is increasing for transfer of image data of a large capacity of 4 kilobytes to 6 megabytes or so by way of a very high speed transmission line of 10 gigabits/second or so. It has been proposed to employ an optical space switch device as a variably interconnectable cross connecting device to achieve such transfer.
Meanwhile, attention has been and is paid to an optical space switch device as it can be utilized also for other applications wherein a subsystem such as a coupling network between processors and/or memories of a parallel processing computer or a multistage switch for an ATM exchange is realized with optical channels.
As an optical space switch device of the type mentioned, an optical switch has conventionally been proposed and is disclosed, for example, in APPLIED OPTITCS, Vol. 29, No. 26, pp. 3848-3854, Sep. 10, 1990, which includes a combination of a polarization controlling element formed from a liquid crystal material and a device providing a polarized light separating function and employing a hologram.
Another optical switch has been proposed and is disclosed in Photonic Switching II, Proceedings of the International Topical Meeting, Kobe, Japan, Apr. 12-14, 1990, which includes a combination of a polarization controlling planar element such as a liquid crystal panel for receiving a planar input and a routing element employing a birefringent crystal.
Also an optical space switch has been proposed and is disclosed in Photonic Switching, Vol. 8, Proceedings of the International Topical Meeting, Salt Lake City, Utah, Mar. 6-8, 1991, which includes a first reflecting block including a combination of a polarized light separator, a polarization controller, a quarter-wave (.lambda./4) plate and an optical path modifying element, and a second reflecting block including a quarter-wave plate and a reflecting mirror.
Also an optical crossbar switch device has been proposed wherein optical crossbar switches are disposed in a matrix on a waveguide formed on a dielectric (LiNbO.sub.3) substrate.
However, such conventional optical space switch devices as described above are disadvantageous in that they are complicated in structure and expensive and require, because a polishing step is necessary, a great number of working steps.
Further, while the conventional optical space switch device of the type which includes a first reflecting block including a polarized light separator, a polarization controller, a quarter-wave plate and an optical path modifying element and a second reflecting block including a quarter-wave plate and a reflecting mirror employs a prism array as the optical path modifying element, when it is designed so as to receive multichannel beams as an input thereto, the prism array has a correspondingly great size, and besides there is the possibility that the insertion loss and the crosstalk may be increased by an increase of the number of optical paths and an increase of the difference among lengths of the optical paths by beam routes. It is further disadvantageous in that it can assume only 2-input 2-output configuration.
Also there is a disadvantage that it is impossible to handle a two-dimensional signal (planar input).